ping_triggers outlive packet retention (1884 of 3682 on staging) — confirm it is intended for ping-score history, document or prune #241

Relates to #215, #222

Observation

The post-migration verification of #222 on staging found ping_triggers rows whose tx_id no longer exists in transmissions. The pre-migration snapshot has the same count, so this does not come from the migration.

The orphaned rows span first_seen 2026-07-14 to 2026-09-05. The oldest remaining transmission is from 2026-09-05. In other words, every orphan is older than the packet retention window.

Cause. PruneOldPackets in cmd/ingestor/maintenance.go deletes observations and route_mask_changes together with an aged transmission, but leaves ping_triggers in place. PruneOrphanRouteMaskChanges exists for route_mask_changes. There is nothing equivalent for ping_triggers.

Question: intentional or a gap?

This may be by design. cmd/server/ping_score_history.go describes the ping-score history store as "the ONLY remaining source for that ping's contribution to the all-time records" once packets are pruned, and the history engine reconciles against ping_triggers. If the all-time ping records rely on ping_triggers outliving the packets, these rows are not orphans in the harmful sense.

Tasks

• Confirm from the ping-score history code and its tests whether ping_triggers must outlive packet retention. Check what the engine does with a trigger whose transmission is gone (DataPruned, Unscorable).
• If intentional: document it at PruneOldPackets and in the schema notes. Note it in deploy-verification guidance, so that "orphan ping_triggers" is not reported as an integrity error. Decide whether an upper bound is needed. Today the table grows by roughly 100 rows a day on staging.
• If not intentional: prune ping_triggers with the transmission in PruneOldPackets, or add PruneOrphanPingTriggers like the route_mask_changes one, with a test. First confirm that the ping-score history keeps the all-time records without them.

Acceptance

• The intended lifetime of ping_triggers is decided, documented and pinned by a test.
• The deploy verification for content-hash migrations (fix(store): move content-hash migration writes to the ingestor and merge duplicates in memory (#215) #222) distinguishes intended retained triggers from real orphans.